A video frame is frequently transmitted in an interlaced format, where the first line zero and each subsequent even-numbered line are sent first, covering every other line of the screen from the top down, and then line "one" and each subsequent odd-numbered line are sent, to fill in the gaps in the screen, again from the top down. This maintains a transmission time which is below the threshold for perceiving a flicker on the screen.
The assignee of the present invention developed a digital X-ray image processing system which digitizes successive frames of video data representing X-ray images, and manipulates data representative of the images for various purposes such as image enhancement, incremental subtraction, display buffering and the like. After the digital data has been processed, it is employed to control a CRT readout console which displays the visually enhanced digital X-ray images for diagnostic purposes. Interlace video data generated by the T.V. camera is converted to a non-interlace, i.e., a sequential format where the lines are in order, format before the data processing is carried out. After insertion of the digitized frame into a first digital storage device, the lines could be rearranged by inserting them in the proper order into a second storage device, which would contain the non-interlaced frame image. However, it is deemed desirable to eliminate the use of more than one frame memory, and yet provide real time conversion from the interlace to the non-interlace format. This objective is attained in accordance with the present invention by taking advantage of the fact that the number of lines per frame are generally an integral power of 2.